1. Field of the Invention
The present invention relates to a semiconductor memory device and an operation method thereof. More particularly, the present invention pertains to a semiconductor memory device having a DRAM cell mode and a non-volatile memory cell mode, and an operation method thereof.
2. Description of Related Art
Semiconductor memory devices include non-volatile memory devices, e.g., a flash memory, and volatile memory devices, e.g., a dynamic random access memory (DRAM). The flash memory may maintain data stored in a memory cell even when power supply is turned off. However, since the flash memory may require a large time period to write or erase data, the flash memory may not be appropriate for frequent rewriting. The number of cycles of writing or erasing data in the non-volatile memory device may thus be limited.
The DRAM may not maintain data stored in a memory cell when the power supply is turned off. However, since the DRAM requires a short time to rewrite data, there is no limitation in the number of cycles of rewriting data.
Therefore, a semiconductor memory device capable of frequently rewriting data and maintaining the rewritten data for a long time has been desired. That is, a semiconductor memory device having both a non-volatile memory cell region and a DRAM cell region may be advantageous.
One type of semiconductor memory device may include a capacitor. Since the semiconductor memory device including the capacitor may require a region for the capacitor, there may be a limit in improving the integration density. In addition, since the semiconductor memory device including the capacitor may perform a program operation or an erase operation as a non-volatile memory device depending on whether the capacitor stores information or not, its operation method may be complicated.